Can you swear for his honesty?

你能担保他诚实吗？

His friends will swear for his integrity.

他的朋友愿意为他正直的品格作担保。

I could call many people to swear for this method.

我可以请许多人为这个方法担保。

It is totally unacceptable for children to swear.

小孩子骂人是完全不能接受的。

Would you just hold hands and swear that we—Oh no, that wouldn't do for this.

你能不能举起手来，发誓我们——哦，不，这可不行。